I. The Field of the Invention
The present invention relates to systems and methods for processing mixed solid waste to produce recyclable materials and/or to convert refuse into fuels or high value chemicals.
II. The Related Technology
Commercial, industrial, and residential consumers generate large amounts of throw-away and waste products (i.e., municipal solid waste) that need to be handled and disposed of in an environmentally satisfactory manner. Traditionally, municipal solid waste (hereinafter “MSW”) has been disposed of by landfilling or incineration. However, these methods of waste product disposal contaminate the soil, water and air. Environmental restrictions as well as land usage demands for housing have reduced the number of sites available for landfills.
In response, governments and the public have demanded that, wherever possible, recycling systems should be employed to conserve material resources and to reduce pollution problems. Efforts have been made to recover valuable resources such as glass, plastic, paper, aluminum, and ferrous and non-ferrous metals from waste materials. For example, households in many cities are asked to sort their garbage into recyclables (e.g., paper, plastic containers, metal containers and glass containers) and non-recyclables. However, rates of non-compliance and mis-compliance are high. Some people fail to sort their waste at all and other sort it incorrectly, which either shunts recoverable materials into the waste stream or contaminates the recyclable stream with waste materials. Non-compliance and mis-compliance reduce the efficiency of and increases the costs associated with operating recycling systems designed to processed pre-sorted waste.
Some recycling systems attempt to avoid the problems with presorted waste by attempting to recover recyclable materials from mixed waste. However, many of these systems are fraught with the tendency to be highly labor intensive to operate, while offering relatively low recovery rates of recyclables.
The energy balance of many recycling systems is sub-par or, in some cases, negative. Some recycling systems are so inefficient that the processes of recovering, transporting, and recycling the recyclable materials consumes more energy than could be saved by simply landfilling the garbage and making new products from raw materials. In other cases so little of the recyclable materials are recovered that the problems with waste stream disposal go essentially unmitigated.